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	$132.96	10.619%	$147.079	$147.08	$147.10	$147.10
Purchase #2	$49.35	8.245%	$53.4189	$53.42	$53.40	$53.40
Purchase #3	$67.76	7.477%	$72.8264	$72.83	$72.85	$72.80
Purchase #4	$122.60	11.136%	$136.2527	$136.25	$136.25	$136.30
Purchase #5	$187.61	13.369%	$212.6916	$212.69	$212.70	$212.70
Purchase #6	$58.45	3.159%	$60.2964	$60.30	$60.30	$60.30
Purchase #7	$77.27	6.816%	$82.5367	$82.54	$82.55	$82.50
7 purchase totals =	$696.00		$765.1017	$765.11	$765.15	$765.10