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	$165.34	5.549%	$174.5147	$174.51	$174.50	$174.50
Purchase #2	$147.48	13.489%	$167.3736	$167.37	$167.35	$167.40
Purchase #3	$136.54	4.371%	$142.5082	$142.51	$142.50	$142.50
Purchase #4	$242.37	3.288%	$250.3391	$250.34	$250.35	$250.30
Purchase #5	$220.86	4.374%	$230.5204	$230.52	$230.50	$230.50
Purchase #6	$219.58	12.285%	$246.5554	$246.56	$246.55	$246.60
Purchase #7	$135.31	5.459%	$142.6966	$142.70	$142.70	$142.70
7 purchase totals =	$1,267.48		$1,354.5080	$1,354.51	$1,354.45	$1,354.50