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	$120.49	5.869%	$127.5616	$127.56	$127.55	$127.60
Purchase #2	$106.53	5.673%	$112.5734	$112.57	$112.55	$112.60
Purchase #3	$181.67	9.150%	$198.2928	$198.29	$198.30	$198.30
Purchase #4	$104.99	7.818%	$113.1981	$113.20	$113.20	$113.20
Purchase #5	$229.38	4.103%	$238.7915	$238.79	$238.80	$238.80
Purchase #6	$67.31	4.434%	$70.2945	$70.29	$70.30	$70.30
Purchase #7	$149.83	9.808%	$164.5253	$164.53	$164.55	$164.50
7 purchase totals =	$960.20		$1,025.2372	$1,025.23	$1,025.25	$1,025.30