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	$174.66	12.443%	$196.3929	$196.39	$196.40	$196.40
Purchase #2	$169.99	11.121%	$188.8946	$188.89	$188.90	$188.90
Purchase #3	$24.27	12.682%	$27.3479	$27.35	$27.35	$27.30
Purchase #4	$34.34	8.865%	$37.3842	$37.38	$37.40	$37.40
Purchase #5	$60.91	10.472%	$67.2885	$67.29	$67.30	$67.30
Purchase #6	$131.49	10.292%	$145.023	$145.02	$145.00	$145.00
Purchase #7	$170.67	13.731%	$194.1047	$194.10	$194.10	$194.10
7 purchase totals =	$766.33		$856.4358	$856.42	$856.45	$856.40