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	$10.56	6.675%	$11.2649	$11.26	$11.25	$11.30
Purchase #2	$234.67	6.585%	$250.123	$250.12	$250.10	$250.10
Purchase #3	$97.53	12.569%	$109.7885	$109.79	$109.80	$109.80
Purchase #4	$233.65	5.250%	$245.9166	$245.92	$245.90	$245.90
Purchase #5	$237.26	3.328%	$245.156	$245.16	$245.15	$245.20
Purchase #6	$187.75	3.500%	$194.3213	$194.32	$194.30	$194.30
Purchase #7	$17.54	4.774%	$18.3774	$18.38	$18.40	$18.40
7 purchase totals =	$1,018.96		$1,074.9477	$1,074.95	$1,074.90	$1,075.00