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	$198.56	12.490%	$223.3601	$223.36	$223.35	$223.40
Purchase #2	$152.41	5.327%	$160.5289	$160.53	$160.55	$160.50
Purchase #3	$19.37	13.224%	$21.9315	$21.93	$21.95	$21.90
Purchase #4	$96.95	13.152%	$109.7009	$109.70	$109.70	$109.70
Purchase #5	$116.48	12.607%	$131.1646	$131.16	$131.15	$131.20
Purchase #6	$228.44	4.470%	$238.6513	$238.65	$238.65	$238.70
Purchase #7	$227.91	6.604%	$242.9612	$242.96	$242.95	$243.00
7 purchase totals =	$1,040.12		$1,128.2985	$1,128.29	$1,128.30	$1,128.40