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	$58.33	6.449%	$62.0917	$62.09	$62.10	$62.10
Purchase #2	$196.34	12.664%	$221.2045	$221.20	$221.20	$221.20
Purchase #3	$225.82	12.581%	$254.2304	$254.23	$254.25	$254.20
Purchase #4	$20.59	4.514%	$21.5194	$21.52	$21.50	$21.50
Purchase #5	$142.85	9.674%	$156.6693	$156.67	$156.65	$156.70
Purchase #6	$248.50	6.860%	$265.5471	$265.55	$265.55	$265.50
Purchase #7	$115.88	13.492%	$131.5145	$131.51	$131.50	$131.50
7 purchase totals =	$1,008.31		$1,112.7769	$1,112.77	$1,112.75	$1,112.70