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	$200.67	11.288%	$223.3216	$223.32	$223.30	$223.30
Purchase #2	$94.91	6.549%	$101.1257	$101.13	$101.15	$101.10
Purchase #3	$191.52	12.776%	$215.9886	$215.99	$216.00	$216.00
Purchase #4	$99.91	5.217%	$105.1223	$105.12	$105.10	$105.10
Purchase #5	$100.58	10.515%	$111.156	$111.16	$111.15	$111.20
Purchase #6	$248.95	7.804%	$268.3781	$268.38	$268.40	$268.40
Purchase #7	$106.73	11.525%	$119.0306	$119.03	$119.05	$119.00
7 purchase totals =	$1,043.27		$1,144.1229	$1,144.13	$1,144.15	$1,144.10