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	$65.86	10.419%	$72.722	$72.72	$72.70	$72.70
Purchase #2	$184.30	4.759%	$193.0708	$193.07	$193.05	$193.10
Purchase #3	$219.89	4.568%	$229.9346	$229.93	$229.95	$229.90
Purchase #4	$211.78	7.723%	$228.1358	$228.14	$228.15	$228.10
Purchase #5	$169.91	10.862%	$188.3656	$188.37	$188.35	$188.40
Purchase #6	$162.96	5.728%	$172.2943	$172.29	$172.30	$172.30
Purchase #7	$5.83	4.545%	$6.095	$6.10	$6.10	$6.10
7 purchase totals =	$1,020.53		$1,090.6181	$1,090.62	$1,090.60	$1,090.60