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	$171.41	4.332%	$178.8355	$178.84	$178.85	$178.80
Purchase #2	$218.68	10.282%	$241.1647	$241.16	$241.15	$241.20
Purchase #3	$193.50	9.132%	$211.1704	$211.17	$211.15	$211.20
Purchase #4	$223.73	7.147%	$239.72	$239.72	$239.70	$239.70
Purchase #5	$102.61	6.247%	$109.02	$109.02	$109.00	$109.00
Purchase #6	$96.70	7.339%	$103.7968	$103.80	$103.80	$103.80
Purchase #7	$53.69	10.681%	$59.4246	$59.42	$59.40	$59.40
7 purchase totals =	$1,060.32		$1,143.1320	$1,143.13	$1,143.05	$1,143.10