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	$171.31	13.437%	$194.3289	$194.33	$194.35	$194.30
Purchase #2	$30.53	9.380%	$33.3937	$33.39	$33.40	$33.40
Purchase #3	$65.79	7.331%	$70.6131	$70.61	$70.60	$70.60
Purchase #4	$217.44	9.811%	$238.773	$238.77	$238.75	$238.80
Purchase #5	$233.75	13.152%	$264.4928	$264.49	$264.50	$264.50
Purchase #6	$83.51	10.289%	$92.1023	$92.10	$92.10	$92.10
Purchase #7	$134.29	12.379%	$150.9138	$150.91	$150.90	$150.90
7 purchase totals =	$936.62		$1,044.6176	$1,044.60	$1,044.60	$1,044.60