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	$198.45	11.479%	$221.2301	$221.23	$221.25	$221.20
Purchase #2	$57.80	8.722%	$62.8413	$62.84	$62.85	$62.80
Purchase #3	$66.69	5.569%	$70.404	$70.40	$70.40	$70.40
Purchase #4	$250.33	11.734%	$279.7037	$279.70	$279.70	$279.70
Purchase #5	$74.96	6.829%	$80.079	$80.08	$80.10	$80.10
Purchase #6	$168.39	11.810%	$188.2769	$188.28	$188.30	$188.30
Purchase #7	$165.59	3.778%	$171.846	$171.85	$171.85	$171.80
7 purchase totals =	$982.21		$1,074.3810	$1,074.38	$1,074.45	$1,074.30