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	$30.95	3.599%	$32.0639	$32.06	$32.05	$32.10
Purchase #2	$89.36	11.205%	$99.3728	$99.37	$99.35	$99.40
Purchase #3	$224.37	7.107%	$240.316	$240.32	$240.30	$240.30
Purchase #4	$223.79	13.581%	$254.1829	$254.18	$254.20	$254.20
Purchase #5	$47.41	13.245%	$53.6895	$53.69	$53.70	$53.70
Purchase #6	$112.66	5.832%	$119.2303	$119.23	$119.25	$119.20
Purchase #7	$234.59	5.752%	$248.0836	$248.08	$248.10	$248.10
7 purchase totals =	$963.13		$1,046.9390	$1,046.93	$1,046.95	$1,047.00