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	$147.89	5.761%	$156.4099	$156.41	$156.40	$156.40
Purchase #2	$184.46	4.802%	$193.3178	$193.32	$193.30	$193.30
Purchase #3	$102.46	11.470%	$114.2122	$114.21	$114.20	$114.20
Purchase #4	$91.98	8.568%	$99.8608	$99.86	$99.85	$99.90
Purchase #5	$94.35	6.713%	$100.6837	$100.68	$100.70	$100.70
Purchase #6	$85.73	3.359%	$88.6097	$88.61	$88.60	$88.60
Purchase #7	$175.28	11.684%	$195.7597	$195.76	$195.75	$195.80
7 purchase totals =	$882.15		$948.8538	$948.85	$948.80	$948.90