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	$167.28	11.435%	$186.4085	$186.41	$186.40	$186.40
Purchase #2	$69.92	5.425%	$73.7132	$73.71	$73.70	$73.70
Purchase #3	$38.61	8.563%	$41.9162	$41.92	$41.90	$41.90
Purchase #4	$147.82	3.136%	$152.4556	$152.46	$152.45	$152.50
Purchase #5	$114.25	11.734%	$127.6561	$127.66	$127.65	$127.70
Purchase #6	$228.65	6.401%	$243.2859	$243.29	$243.30	$243.30
Purchase #7	$159.48	6.166%	$169.3135	$169.31	$169.30	$169.30
7 purchase totals =	$926.01		$994.7490	$994.76	$994.70	$994.80