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	$45.79	3.567%	$47.4233	$47.42	$47.40	$47.40
Purchase #2	$114.31	11.235%	$127.1527	$127.15	$127.15	$127.20
Purchase #3	$65.26	9.501%	$71.4604	$71.46	$71.45	$71.50
Purchase #4	$91.87	5.427%	$96.8558	$96.86	$96.85	$96.90
Purchase #5	$62.81	4.349%	$65.5416	$65.54	$65.55	$65.50
Purchase #6	$86.44	5.745%	$91.406	$91.41	$91.40	$91.40
Purchase #7	$36.80	12.139%	$41.2672	$41.27	$41.25	$41.30
7 purchase totals =	$503.28		$541.1070	$541.11	$541.05	$541.20