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	$168.25	6.218%	$178.7118	$178.71	$178.70	$178.70
Purchase #2	$175.83	7.420%	$188.8766	$188.88	$188.90	$188.90
Purchase #3	$136.95	3.752%	$142.0884	$142.09	$142.10	$142.10
Purchase #4	$155.25	7.803%	$167.3642	$167.36	$167.35	$167.40
Purchase #5	$153.29	4.789%	$160.6311	$160.63	$160.65	$160.60
Purchase #6	$248.85	6.218%	$264.3235	$264.32	$264.30	$264.30
Purchase #7	$8.44	13.265%	$9.5596	$9.56	$9.55	$9.60
7 purchase totals =	$1,046.86		$1,111.5552	$1,111.55	$1,111.55	$1,111.60