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	$54.98	11.385%	$61.2395	$61.24	$61.25	$61.20
Purchase #2	$53.66	10.446%	$59.2653	$59.27	$59.25	$59.30
Purchase #3	$235.41	4.251%	$245.4173	$245.42	$245.40	$245.40
Purchase #4	$199.53	6.411%	$212.3219	$212.32	$212.30	$212.30
Purchase #5	$45.91	6.840%	$49.0502	$49.05	$49.05	$49.10
Purchase #6	$249.73	5.644%	$263.8248	$263.82	$263.80	$263.80
Purchase #7	$186.67	12.365%	$209.7517	$209.75	$209.75	$209.80
7 purchase totals =	$1,025.89		$1,100.8707	$1,100.87	$1,100.80	$1,100.90