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	$54.69	10.136%	$60.2334	$60.23	$60.25	$60.20
Purchase #2	$19.56	6.822%	$20.8944	$20.89	$20.90	$20.90
Purchase #3	$134.89	5.448%	$142.2388	$142.24	$142.25	$142.20
Purchase #4	$47.96	13.251%	$54.3152	$54.32	$54.30	$54.30
Purchase #5	$218.72	9.402%	$239.2841	$239.28	$239.30	$239.30
Purchase #6	$29.79	9.697%	$32.6787	$32.68	$32.70	$32.70
Purchase #7	$216.33	11.293%	$240.7601	$240.76	$240.75	$240.80
7 purchase totals =	$721.94		$790.4047	$790.40	$790.45	$790.40