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	$204.92	11.459%	$228.4018	$228.40	$228.40	$228.40
Purchase #2	$101.83	10.698%	$112.7238	$112.72	$112.70	$112.70
Purchase #3	$195.60	7.150%	$209.5854	$209.59	$209.60	$209.60
Purchase #4	$99.30	6.408%	$105.6631	$105.66	$105.65	$105.70
Purchase #5	$171.58	4.675%	$179.6014	$179.60	$179.60	$179.60
Purchase #6	$149.51	4.279%	$155.9075	$155.91	$155.90	$155.90
Purchase #7	$144.81	13.737%	$164.7025	$164.70	$164.70	$164.70
7 purchase totals =	$1,067.55		$1,156.5855	$1,156.58	$1,156.55	$1,156.60