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	$235.84	10.722%	$261.1268	$261.13	$261.15	$261.10
Purchase #2	$147.91	12.797%	$166.838	$166.84	$166.85	$166.80
Purchase #3	$184.62	8.792%	$200.8518	$200.85	$200.85	$200.90
Purchase #4	$202.29	12.845%	$228.2742	$228.27	$228.25	$228.30
Purchase #5	$41.54	3.773%	$43.1073	$43.11	$43.10	$43.10
Purchase #6	$62.41	7.587%	$67.145	$67.15	$67.15	$67.10
Purchase #7	$236.81	9.819%	$260.0624	$260.06	$260.05	$260.10
7 purchase totals =	$1,111.42		$1,227.4055	$1,227.41	$1,227.40	$1,227.40