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	$198.81	9.818%	$218.3292	$218.33	$218.35	$218.30
Purchase #2	$161.56	12.600%	$181.9166	$181.92	$181.90	$181.90
Purchase #3	$49.76	6.744%	$53.1158	$53.12	$53.10	$53.10
Purchase #4	$240.69	4.325%	$251.0998	$251.10	$251.10	$251.10
Purchase #5	$136.81	10.682%	$151.424	$151.42	$151.40	$151.40
Purchase #6	$93.70	6.179%	$99.4897	$99.49	$99.50	$99.50
Purchase #7	$157.89	10.804%	$174.9484	$174.95	$174.95	$174.90
7 purchase totals =	$1,039.22		$1,130.3235	$1,130.33	$1,130.30	$1,130.20