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	$226.41	3.822%	$235.0634	$235.06	$235.05	$235.10
Purchase #2	$115.88	10.341%	$127.8632	$127.86	$127.85	$127.90
Purchase #3	$26.94	6.348%	$28.6502	$28.65	$28.65	$28.70
Purchase #4	$77.75	5.363%	$81.9197	$81.92	$81.90	$81.90
Purchase #5	$81.33	11.647%	$90.8025	$90.80	$90.80	$90.80
Purchase #6	$159.73	5.335%	$168.2516	$168.25	$168.25	$168.30
Purchase #7	$86.98	6.769%	$92.8677	$92.87	$92.85	$92.90
7 purchase totals =	$775.02		$825.4183	$825.41	$825.35	$825.60