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	$91.58	7.454%	$98.4064	$98.41	$98.40	$98.40
Purchase #2	$229.69	9.183%	$250.7824	$250.78	$250.80	$250.80
Purchase #3	$236.71	12.370%	$265.991	$265.99	$266.00	$266.00
Purchase #4	$28.43	10.375%	$31.3796	$31.38	$31.40	$31.40
Purchase #5	$188.88	11.426%	$210.4614	$210.46	$210.45	$210.50
Purchase #6	$196.43	11.123%	$218.2789	$218.28	$218.30	$218.30
Purchase #7	$29.70	11.293%	$33.054	$33.05	$33.05	$33.10
7 purchase totals =	$1,001.42		$1,108.3537	$1,108.35	$1,108.40	$1,108.50