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	$161.51	7.839%	$174.1708	$174.17	$174.15	$174.20
Purchase #2	$217.78	4.391%	$227.3427	$227.34	$227.35	$227.30
Purchase #3	$133.91	10.297%	$147.6987	$147.70	$147.70	$147.70
Purchase #4	$168.28	10.368%	$185.7273	$185.73	$185.75	$185.70
Purchase #5	$44.51	4.801%	$46.6469	$46.65	$46.65	$46.60
Purchase #6	$247.51	6.435%	$263.4373	$263.44	$263.45	$263.40
Purchase #7	$83.93	6.499%	$89.3846	$89.38	$89.40	$89.40
7 purchase totals =	$1,057.43		$1,134.4083	$1,134.41	$1,134.45	$1,134.30