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	$152.91	9.119%	$166.8539	$166.85	$166.85	$166.90
Purchase #2	$100.58	10.632%	$111.2737	$111.27	$111.25	$111.30
Purchase #3	$171.63	8.524%	$186.2597	$186.26	$186.25	$186.30
Purchase #4	$162.58	10.315%	$179.3501	$179.35	$179.35	$179.40
Purchase #5	$43.63	11.564%	$48.6754	$48.68	$48.70	$48.70
Purchase #6	$161.73	12.172%	$181.4158	$181.42	$181.40	$181.40
Purchase #7	$183.41	9.453%	$200.7477	$200.75	$200.75	$200.70
7 purchase totals =	$976.47		$1,074.5763	$1,074.58	$1,074.55	$1,074.70