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	$234.73	6.568%	$250.1471	$250.15	$250.15	$250.10
Purchase #2	$85.79	8.570%	$93.1422	$93.14	$93.15	$93.10
Purchase #3	$178.28	7.650%	$191.9184	$191.92	$191.90	$191.90
Purchase #4	$136.65	11.615%	$152.5219	$152.52	$152.50	$152.50
Purchase #5	$184.62	5.489%	$194.7538	$194.75	$194.75	$194.80
Purchase #6	$114.29	8.278%	$123.7509	$123.75	$123.75	$123.80
Purchase #7	$28.44	13.614%	$32.3118	$32.31	$32.30	$32.30
7 purchase totals =	$962.80		$1,038.5461	$1,038.54	$1,038.50	$1,038.50