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	$86.81	9.207%	$94.8026	$94.80	$94.80	$94.80
Purchase #2	$240.43	9.864%	$264.146	$264.15	$264.15	$264.10
Purchase #3	$180.91	4.169%	$188.4521	$188.45	$188.45	$188.50
Purchase #4	$85.43	12.164%	$95.8217	$95.82	$95.80	$95.80
Purchase #5	$236.31	12.201%	$265.1422	$265.14	$265.15	$265.10
Purchase #6	$33.28	12.344%	$37.3881	$37.39	$37.40	$37.40
Purchase #7	$129.69	13.614%	$147.346	$147.35	$147.35	$147.30
7 purchase totals =	$992.86		$1,093.0987	$1,093.10	$1,093.10	$1,093.00