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	$47.86	12.237%	$53.7166	$53.72	$53.70	$53.70
Purchase #2	$212.65	5.328%	$223.98	$223.98	$224.00	$224.00
Purchase #3	$39.95	8.280%	$43.2579	$43.26	$43.25	$43.30
Purchase #4	$49.54	6.364%	$52.6927	$52.69	$52.70	$52.70
Purchase #5	$155.42	6.712%	$165.8518	$165.85	$165.85	$165.90
Purchase #6	$138.65	5.791%	$146.6792	$146.68	$146.70	$146.70
Purchase #7	$90.76	6.404%	$96.5723	$96.57	$96.55	$96.60
7 purchase totals =	$734.83		$782.7505	$782.75	$782.75	$782.90