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	$185.57	7.280%	$199.0795	$199.08	$199.10	$199.10
Purchase #2	$154.66	12.663%	$174.2446	$174.24	$174.25	$174.20
Purchase #3	$173.79	13.520%	$197.2864	$197.29	$197.30	$197.30
Purchase #4	$116.63	13.673%	$132.5768	$132.58	$132.60	$132.60
Purchase #5	$79.32	12.616%	$89.327	$89.33	$89.35	$89.30
Purchase #6	$144.96	7.449%	$155.7581	$155.76	$155.75	$155.80
Purchase #7	$54.87	9.139%	$59.8846	$59.88	$59.90	$59.90
7 purchase totals =	$909.80		$1,008.1570	$1,008.16	$1,008.25	$1,008.20