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	$64.57	11.685%	$72.115	$72.12	$72.10	$72.10
Purchase #2	$160.58	12.459%	$180.5867	$180.59	$180.60	$180.60
Purchase #3	$121.95	7.150%	$130.6694	$130.67	$130.65	$130.70
Purchase #4	$19.33	13.245%	$21.8903	$21.89	$21.90	$21.90
Purchase #5	$41.27	5.707%	$43.6253	$43.63	$43.65	$43.60
Purchase #6	$218.57	4.744%	$228.939	$228.94	$228.95	$228.90
Purchase #7	$104.99	4.260%	$109.4626	$109.46	$109.45	$109.50
7 purchase totals =	$731.26		$787.2883	$787.30	$787.30	$787.30