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	$123.40	6.391%	$131.2865	$131.29	$131.30	$131.30
Purchase #2	$80.91	7.465%	$86.9499	$86.95	$86.95	$86.90
Purchase #3	$144.77	13.592%	$164.4471	$164.45	$164.45	$164.40
Purchase #4	$202.87	13.590%	$230.44	$230.44	$230.45	$230.40
Purchase #5	$66.34	9.219%	$72.4559	$72.46	$72.45	$72.50
Purchase #6	$179.72	9.129%	$196.1266	$196.13	$196.15	$196.10
Purchase #7	$232.28	5.786%	$245.7197	$245.72	$245.70	$245.70
7 purchase totals =	$1,030.29		$1,127.4257	$1,127.44	$1,127.45	$1,127.30