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	$70.86	3.355%	$73.2374	$73.24	$73.25	$73.20
Purchase #2	$224.89	7.228%	$241.145	$241.15	$241.15	$241.10
Purchase #3	$105.40	11.346%	$117.3587	$117.36	$117.35	$117.40
Purchase #4	$117.47	8.469%	$127.4185	$127.42	$127.40	$127.40
Purchase #5	$93.67	6.747%	$99.9899	$99.99	$100.00	$100.00
Purchase #6	$43.48	11.165%	$48.3345	$48.33	$48.35	$48.30
Purchase #7	$93.48	7.785%	$100.7574	$100.76	$100.75	$100.80
7 purchase totals =	$749.25		$808.2414	$808.25	$808.25	$808.20