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	$119.56	6.459%	$127.2824	$127.28	$127.30	$127.30
Purchase #2	$169.69	11.123%	$188.5646	$188.56	$188.55	$188.60
Purchase #3	$46.69	13.415%	$52.9535	$52.95	$52.95	$53.00
Purchase #4	$111.82	10.865%	$123.9692	$123.97	$123.95	$124.00
Purchase #5	$181.86	7.228%	$195.0048	$195.00	$195.00	$195.00
Purchase #6	$153.98	4.525%	$160.9476	$160.95	$160.95	$160.90
Purchase #7	$57.99	6.441%	$61.7251	$61.73	$61.75	$61.70
7 purchase totals =	$841.59		$910.4472	$910.44	$910.45	$910.50