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	$91.53	5.751%	$96.7939	$96.79	$96.80	$96.80
Purchase #2	$27.85	12.506%	$31.3329	$31.33	$31.35	$31.30
Purchase #3	$36.31	9.213%	$39.6552	$39.66	$39.65	$39.70
Purchase #4	$189.34	11.152%	$210.4552	$210.46	$210.45	$210.50
Purchase #5	$220.28	10.802%	$244.0746	$244.07	$244.05	$244.10
Purchase #6	$233.25	3.260%	$240.854	$240.85	$240.85	$240.90
Purchase #7	$210.95	8.155%	$228.153	$228.15	$228.15	$228.20
7 purchase totals =	$1,009.51		$1,091.3188	$1,091.31	$1,091.30	$1,091.50