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	$74.74	4.428%	$78.0495	$78.05	$78.05	$78.00
Purchase #2	$91.28	5.250%	$96.0722	$96.07	$96.05	$96.10
Purchase #3	$24.33	3.213%	$25.1117	$25.11	$25.10	$25.10
Purchase #4	$233.90	13.561%	$265.6192	$265.62	$265.60	$265.60
Purchase #5	$240.32	5.203%	$252.8238	$252.82	$252.80	$252.80
Purchase #6	$137.71	4.285%	$143.6109	$143.61	$143.60	$143.60
Purchase #7	$52.58	3.471%	$54.4051	$54.41	$54.40	$54.40
7 purchase totals =	$854.86		$915.6924	$915.69	$915.60	$915.60