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	$10.73	5.556%	$11.3262	$11.33	$11.35	$11.30
Purchase #2	$229.81	13.444%	$260.7057	$260.71	$260.70	$260.70
Purchase #3	$220.41	3.643%	$228.4395	$228.44	$228.45	$228.40
Purchase #4	$76.75	7.699%	$82.659	$82.66	$82.65	$82.70
Purchase #5	$196.83	13.581%	$223.5615	$223.56	$223.55	$223.60
Purchase #6	$156.45	3.814%	$162.417	$162.42	$162.40	$162.40
Purchase #7	$237.89	13.122%	$269.1059	$269.11	$269.10	$269.10
7 purchase totals =	$1,128.87		$1,238.2148	$1,238.23	$1,238.20	$1,238.20