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	$72.42	7.841%	$78.0985	$78.10	$78.10	$78.10
Purchase #2	$93.72	7.638%	$100.8783	$100.88	$100.90	$100.90
Purchase #3	$230.59	6.268%	$245.0434	$245.04	$245.05	$245.00
Purchase #4	$147.49	13.670%	$167.6519	$167.65	$167.65	$167.70
Purchase #5	$13.50	5.183%	$14.1997	$14.20	$14.20	$14.20
Purchase #6	$205.96	4.442%	$215.1087	$215.11	$215.10	$215.10
Purchase #7	$236.73	11.256%	$263.3763	$263.38	$263.40	$263.40
7 purchase totals =	$1,000.41		$1,084.3568	$1,084.36	$1,084.40	$1,084.40