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	$98.52	3.713%	$102.178	$102.18	$102.20	$102.20
Purchase #2	$104.29	12.809%	$117.6485	$117.65	$117.65	$117.60
Purchase #3	$146.27	4.224%	$152.4484	$152.45	$152.45	$152.40
Purchase #4	$90.77	6.381%	$96.562	$96.56	$96.55	$96.60
Purchase #5	$120.52	6.591%	$128.4635	$128.46	$128.45	$128.50
Purchase #6	$49.74	6.496%	$52.9711	$52.97	$52.95	$53.00
Purchase #7	$155.77	6.709%	$166.2206	$166.22	$166.20	$166.20
7 purchase totals =	$765.88		$816.4921	$816.49	$816.45	$816.50