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	$57.90	11.276%	$64.4288	$64.43	$64.45	$64.40
Purchase #2	$128.46	6.675%	$137.0347	$137.03	$137.05	$137.00
Purchase #3	$185.61	12.794%	$209.3569	$209.36	$209.35	$209.40
Purchase #4	$198.72	10.398%	$219.3829	$219.38	$219.40	$219.40
Purchase #5	$133.67	3.275%	$138.0477	$138.05	$138.05	$138.00
Purchase #6	$91.84	11.813%	$102.6891	$102.69	$102.70	$102.70
Purchase #7	$200.53	11.500%	$223.591	$223.59	$223.60	$223.60
7 purchase totals =	$996.73		$1,094.5311	$1,094.53	$1,094.60	$1,094.50