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	$68.63	7.139%	$73.5295	$73.53	$73.55	$73.50
Purchase #2	$141.31	7.577%	$152.0171	$152.02	$152.00	$152.00
Purchase #3	$163.73	12.106%	$183.5512	$183.55	$183.55	$183.60
Purchase #4	$246.49	9.191%	$269.1449	$269.14	$269.15	$269.10
Purchase #5	$120.33	5.857%	$127.3777	$127.38	$127.40	$127.40
Purchase #6	$235.40	8.798%	$256.1105	$256.11	$256.10	$256.10
Purchase #7	$36.88	4.837%	$38.6639	$38.66	$38.65	$38.70
7 purchase totals =	$1,012.77		$1,100.3948	$1,100.39	$1,100.40	$1,100.40