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	$208.35	9.303%	$227.7328	$227.73	$227.75	$227.70
Purchase #2	$37.46	10.285%	$41.3128	$41.31	$41.30	$41.30
Purchase #3	$55.61	11.251%	$61.8667	$61.87	$61.85	$61.90
Purchase #4	$29.64	12.689%	$33.401	$33.40	$33.40	$33.40
Purchase #5	$122.52	4.218%	$127.6879	$127.69	$127.70	$127.70
Purchase #6	$113.98	12.290%	$127.9881	$127.99	$128.00	$128.00
Purchase #7	$68.51	6.657%	$73.0707	$73.07	$73.05	$73.10
7 purchase totals =	$636.07		$693.0600	$693.06	$693.05	$693.10