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	$227.37	5.797%	$240.5506	$240.55	$240.55	$240.60
Purchase #2	$96.48	8.122%	$104.3161	$104.32	$104.30	$104.30
Purchase #3	$154.25	5.578%	$162.8541	$162.85	$162.85	$162.90
Purchase #4	$250.56	11.501%	$279.3769	$279.38	$279.40	$279.40
Purchase #5	$148.85	9.106%	$162.4043	$162.40	$162.40	$162.40
Purchase #6	$134.26	6.362%	$142.8016	$142.80	$142.80	$142.80
Purchase #7	$244.51	10.753%	$270.8022	$270.80	$270.80	$270.80
7 purchase totals =	$1,256.28		$1,363.1058	$1,363.10	$1,363.10	$1,363.20