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	$164.83	5.449%	$173.8116	$173.81	$173.80	$173.80
Purchase #2	$109.48	6.305%	$116.3827	$116.38	$116.40	$116.40
Purchase #3	$133.51	6.846%	$142.6501	$142.65	$142.65	$142.70
Purchase #4	$79.55	11.564%	$88.7492	$88.75	$88.75	$88.70
Purchase #5	$225.74	11.332%	$251.3209	$251.32	$251.30	$251.30
Purchase #6	$200.90	11.402%	$223.8066	$223.81	$223.80	$223.80
Purchase #7	$10.82	3.407%	$11.1886	$11.19	$11.20	$11.20
7 purchase totals =	$924.83		$1,007.9097	$1,007.91	$1,007.90	$1,007.90