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	$41.76	8.152%	$45.1643	$45.16	$45.15	$45.20
Purchase #2	$69.42	3.437%	$71.806	$71.81	$71.80	$71.80
Purchase #3	$73.63	13.604%	$83.6466	$83.65	$83.65	$83.60
Purchase #4	$195.68	13.609%	$222.3101	$222.31	$222.30	$222.30
Purchase #5	$188.56	10.711%	$208.7567	$208.76	$208.75	$208.80
Purchase #6	$96.62	13.450%	$109.6154	$109.62	$109.60	$109.60
Purchase #7	$16.27	9.804%	$17.8651	$17.87	$17.85	$17.90
7 purchase totals =	$681.94		$759.1642	$759.18	$759.10	$759.20