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	$92.96	12.601%	$104.6739	$104.67	$104.65	$104.70
Purchase #2	$53.49	11.220%	$59.4916	$59.49	$59.50	$59.50
Purchase #3	$202.39	6.560%	$215.6668	$215.67	$215.65	$215.70
Purchase #4	$224.80	6.760%	$239.9965	$240.00	$240.00	$240.00
Purchase #5	$108.54	13.467%	$123.1571	$123.16	$123.15	$123.20
Purchase #6	$53.72	10.419%	$59.3171	$59.32	$59.30	$59.30
Purchase #7	$195.76	12.668%	$220.5589	$220.56	$220.55	$220.60
7 purchase totals =	$931.66		$1,022.8619	$1,022.87	$1,022.80	$1,023.00