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	$144.48	5.528%	$152.4669	$152.47	$152.45	$152.50
Purchase #2	$82.56	4.322%	$86.1282	$86.13	$86.15	$86.10
Purchase #3	$67.68	7.299%	$72.62	$72.62	$72.60	$72.60
Purchase #4	$233.64	4.125%	$243.2777	$243.28	$243.30	$243.30
Purchase #5	$99.96	9.860%	$109.8161	$109.82	$109.80	$109.80
Purchase #6	$223.57	9.275%	$244.3061	$244.31	$244.30	$244.30
Purchase #7	$214.35	3.244%	$221.3035	$221.30	$221.30	$221.30
7 purchase totals =	$1,066.24		$1,129.9185	$1,129.93	$1,129.90	$1,129.90