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	$100.60	4.650%	$105.2779	$105.28	$105.30	$105.30
Purchase #2	$79.61	3.407%	$82.3223	$82.32	$82.30	$82.30
Purchase #3	$193.41	7.758%	$208.4147	$208.41	$208.40	$208.40
Purchase #4	$162.25	7.110%	$173.786	$173.79	$173.80	$173.80
Purchase #5	$194.32	10.700%	$215.1122	$215.11	$215.10	$215.10
Purchase #6	$180.98	4.410%	$188.9612	$188.96	$188.95	$189.00
Purchase #7	$215.94	9.829%	$237.1647	$237.16	$237.15	$237.20
7 purchase totals =	$1,127.11		$1,211.0390	$1,211.03	$1,211.00	$1,211.10