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	$145.60	11.425%	$162.2348	$162.23	$162.25	$162.20
Purchase #2	$54.68	9.126%	$59.6701	$59.67	$59.65	$59.70
Purchase #3	$133.38	11.277%	$148.4213	$148.42	$148.40	$148.40
Purchase #4	$67.55	6.195%	$71.7347	$71.73	$71.75	$71.70
Purchase #5	$213.80	3.871%	$222.0762	$222.08	$222.10	$222.10
Purchase #6	$211.91	4.745%	$221.9651	$221.97	$221.95	$222.00
Purchase #7	$117.28	11.679%	$130.9771	$130.98	$131.00	$131.00
7 purchase totals =	$944.20		$1,017.0793	$1,017.08	$1,017.10	$1,017.10