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	$202.69	10.471%	$223.9137	$223.91	$223.90	$223.90
Purchase #2	$65.93	10.199%	$72.6542	$72.65	$72.65	$72.70
Purchase #3	$150.26	9.625%	$164.7225	$164.72	$164.70	$164.70
Purchase #4	$149.77	7.232%	$160.6014	$160.60	$160.60	$160.60
Purchase #5	$85.59	10.192%	$94.3133	$94.31	$94.30	$94.30
Purchase #6	$98.54	9.581%	$107.9811	$107.98	$108.00	$108.00
Purchase #7	$26.55	4.374%	$27.7113	$27.71	$27.70	$27.70
7 purchase totals =	$779.33		$851.8975	$851.88	$851.85	$851.90