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	$82.57	8.676%	$89.7338	$89.73	$89.75	$89.70
Purchase #2	$198.28	8.609%	$215.3499	$215.35	$215.35	$215.30
Purchase #3	$216.46	5.678%	$228.7506	$228.75	$228.75	$228.80
Purchase #4	$55.41	11.392%	$61.7223	$61.72	$61.70	$61.70
Purchase #5	$120.49	10.224%	$132.8089	$132.81	$132.80	$132.80
Purchase #6	$127.37	7.816%	$137.3252	$137.33	$137.35	$137.30
Purchase #7	$165.45	10.297%	$182.4864	$182.49	$182.50	$182.50
7 purchase totals =	$966.03		$1,048.1771	$1,048.18	$1,048.20	$1,048.10