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	$172.73	7.469%	$185.6312	$185.63	$185.65	$185.60
Purchase #2	$233.78	7.223%	$250.6659	$250.67	$250.65	$250.70
Purchase #3	$142.57	8.814%	$155.1361	$155.14	$155.15	$155.10
Purchase #4	$87.27	8.305%	$94.5178	$94.52	$94.50	$94.50
Purchase #5	$178.91	11.579%	$199.626	$199.63	$199.65	$199.60
Purchase #6	$66.65	12.611%	$75.0552	$75.06	$75.05	$75.10
Purchase #7	$123.28	6.465%	$131.2501	$131.25	$131.25	$131.30
7 purchase totals =	$1,005.19		$1,091.8823	$1,091.90	$1,091.90	$1,091.90