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	$55.64	7.643%	$59.8926	$59.89	$59.90	$59.90
Purchase #2	$194.64	8.623%	$211.4238	$211.42	$211.40	$211.40
Purchase #3	$170.46	12.296%	$191.4198	$191.42	$191.40	$191.40
Purchase #4	$196.52	11.410%	$218.9429	$218.94	$218.95	$218.90
Purchase #5	$42.79	9.644%	$46.9167	$46.92	$46.90	$46.90
Purchase #6	$141.61	6.715%	$151.1191	$151.12	$151.10	$151.10
Purchase #7	$167.33	7.819%	$180.4135	$180.41	$180.40	$180.40
7 purchase totals =	$968.99		$1,060.1284	$1,060.12	$1,060.05	$1,060.00