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	$117.82	13.546%	$133.7799	$133.78	$133.80	$133.80
Purchase #2	$86.31	11.617%	$96.3366	$96.34	$96.35	$96.30
Purchase #3	$37.69	8.132%	$40.755	$40.76	$40.75	$40.80
Purchase #4	$165.41	3.533%	$171.2539	$171.25	$171.25	$171.30
Purchase #5	$167.72	12.272%	$188.3026	$188.30	$188.30	$188.30
Purchase #6	$51.34	13.309%	$58.1728	$58.17	$58.15	$58.20
Purchase #7	$109.50	9.501%	$119.9036	$119.90	$119.90	$119.90
7 purchase totals =	$735.79		$808.5044	$808.50	$808.50	$808.60