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	$247.59	6.590%	$263.9062	$263.91	$263.90	$263.90
Purchase #2	$80.53	11.554%	$89.8344	$89.83	$89.85	$89.80
Purchase #3	$168.66	11.331%	$187.7709	$187.77	$187.75	$187.80
Purchase #4	$153.87	9.364%	$168.2784	$168.28	$168.30	$168.30
Purchase #5	$171.36	9.758%	$188.0813	$188.08	$188.10	$188.10
Purchase #6	$45.55	10.670%	$50.4102	$50.41	$50.40	$50.40
Purchase #7	$142.77	11.869%	$159.7154	$159.72	$159.70	$159.70
7 purchase totals =	$1,010.33		$1,107.9968	$1,108.00	$1,108.00	$1,108.00