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	$67.97	6.311%	$72.2596	$72.26	$72.25	$72.30
Purchase #2	$53.55	6.242%	$56.8926	$56.89	$56.90	$56.90
Purchase #3	$177.26	8.118%	$191.65	$191.65	$191.65	$191.70
Purchase #4	$44.77	3.399%	$46.2917	$46.29	$46.30	$46.30
Purchase #5	$91.58	8.359%	$99.2352	$99.24	$99.25	$99.20
Purchase #6	$185.89	3.108%	$191.6675	$191.67	$191.65	$191.70
Purchase #7	$232.56	4.844%	$243.8252	$243.83	$243.85	$243.80
7 purchase totals =	$853.58		$901.8218	$901.83	$901.85	$901.90