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	$157.81	5.480%	$166.458	$166.46	$166.45	$166.50
Purchase #2	$98.27	8.419%	$106.5434	$106.54	$106.55	$106.50
Purchase #3	$168.89	6.711%	$180.2242	$180.22	$180.20	$180.20
Purchase #4	$12.79	9.538%	$14.0099	$14.01	$14.00	$14.00
Purchase #5	$218.75	13.424%	$248.115	$248.12	$248.10	$248.10
Purchase #6	$215.29	9.290%	$235.2904	$235.29	$235.30	$235.30
Purchase #7	$114.48	11.732%	$127.9108	$127.91	$127.90	$127.90
7 purchase totals =	$986.28		$1,078.5517	$1,078.55	$1,078.50	$1,078.50