Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$48.63	13.718%	$55.3011	$55.30	$55.30	$55.30
Purchase #2	$102.59	11.211%	$114.0914	$114.09	$114.10	$114.10
Purchase #3	$245.74	3.873%	$255.2575	$255.26	$255.25	$255.30
Purchase #4	$109.72	7.437%	$117.8799	$117.88	$117.90	$117.90
Purchase #5	$248.25	6.452%	$264.2671	$264.27	$264.25	$264.30
Purchase #6	$149.43	12.744%	$168.4734	$168.47	$168.45	$168.50
Purchase #7	$202.74	9.286%	$221.5664	$221.57	$221.55	$221.60
7 purchase totals =	$1,107.10		$1,196.8368	$1,196.84	$1,196.80	$1,197.00