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	$198.53	6.201%	$210.8408	$210.84	$210.85	$210.80
Purchase #2	$239.96	12.480%	$269.907	$269.91	$269.90	$269.90
Purchase #3	$86.33	3.782%	$89.595	$89.60	$89.60	$89.60
Purchase #4	$165.28	9.272%	$180.6048	$180.60	$180.60	$180.60
Purchase #5	$17.86	5.477%	$18.8382	$18.84	$18.85	$18.80
Purchase #6	$155.29	12.681%	$174.9823	$174.98	$175.00	$175.00
Purchase #7	$10.61	6.828%	$11.3345	$11.33	$11.35	$11.30
7 purchase totals =	$873.86		$956.1026	$956.10	$956.15	$956.00