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	$87.78	4.262%	$91.5212	$91.52	$91.50	$91.50
Purchase #2	$183.74	11.704%	$205.2449	$205.24	$205.25	$205.20
Purchase #3	$65.52	9.471%	$71.7254	$71.73	$71.75	$71.70
Purchase #4	$203.82	12.608%	$229.5176	$229.52	$229.50	$229.50
Purchase #5	$172.46	13.768%	$196.2043	$196.20	$196.20	$196.20
Purchase #6	$149.53	13.155%	$169.2007	$169.20	$169.20	$169.20
Purchase #7	$245.66	12.104%	$275.3947	$275.39	$275.40	$275.40
7 purchase totals =	$1,108.51		$1,238.8088	$1,238.80	$1,238.80	$1,238.70