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	$188.36	12.136%	$211.2194	$211.22	$211.20	$211.20
Purchase #2	$19.64	3.253%	$20.2789	$20.28	$20.30	$20.30
Purchase #3	$187.38	13.550%	$212.77	$212.77	$212.75	$212.80
Purchase #4	$123.28	11.667%	$137.6631	$137.66	$137.65	$137.70
Purchase #5	$218.30	5.597%	$230.5183	$230.52	$230.50	$230.50
Purchase #6	$154.94	3.365%	$160.1537	$160.15	$160.15	$160.20
Purchase #7	$190.48	3.185%	$196.5468	$196.55	$196.55	$196.50
7 purchase totals =	$1,082.38		$1,169.1502	$1,169.15	$1,169.10	$1,169.20