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	$67.96	4.489%	$71.0107	$71.01	$71.00	$71.00
Purchase #2	$148.61	6.700%	$158.5669	$158.57	$158.55	$158.60
Purchase #3	$135.27	8.713%	$147.0561	$147.06	$147.05	$147.10
Purchase #4	$91.37	8.777%	$99.3895	$99.39	$99.40	$99.40
Purchase #5	$243.97	11.362%	$271.6899	$271.69	$271.70	$271.70
Purchase #6	$65.30	10.841%	$72.3792	$72.38	$72.40	$72.40
Purchase #7	$194.53	8.368%	$210.8083	$210.81	$210.80	$210.80
7 purchase totals =	$947.01		$1,030.9006	$1,030.91	$1,030.90	$1,031.00