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	$212.31	13.381%	$240.7192	$240.72	$240.70	$240.70
Purchase #2	$147.71	11.627%	$164.8842	$164.88	$164.90	$164.90
Purchase #3	$79.90	3.792%	$82.9298	$82.93	$82.95	$82.90
Purchase #4	$133.91	9.405%	$146.5042	$146.50	$146.50	$146.50
Purchase #5	$127.41	8.415%	$138.1316	$138.13	$138.15	$138.10
Purchase #6	$142.42	8.531%	$154.5699	$154.57	$154.55	$154.60
Purchase #7	$240.61	7.460%	$258.5595	$258.56	$258.55	$258.60
7 purchase totals =	$1,084.27		$1,186.2984	$1,186.29	$1,186.30	$1,186.30