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	$133.99	5.348%	$141.1558	$141.16	$141.15	$141.20
Purchase #2	$88.32	8.447%	$95.7804	$95.78	$95.80	$95.80
Purchase #3	$73.36	11.480%	$81.7817	$81.78	$81.80	$81.80
Purchase #4	$191.69	4.673%	$200.6477	$200.65	$200.65	$200.60
Purchase #5	$247.54	13.671%	$281.3812	$281.38	$281.40	$281.40
Purchase #6	$159.96	13.740%	$181.9385	$181.94	$181.95	$181.90
Purchase #7	$71.83	13.570%	$81.5773	$81.58	$81.60	$81.60
7 purchase totals =	$966.69		$1,064.2626	$1,064.27	$1,064.35	$1,064.30