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	$151.72	12.805%	$171.1477	$171.15	$171.15	$171.10
Purchase #2	$118.88	10.418%	$131.2649	$131.26	$131.25	$131.30
Purchase #3	$35.44	13.256%	$40.1379	$40.14	$40.15	$40.10
Purchase #4	$156.59	11.809%	$175.0817	$175.08	$175.10	$175.10
Purchase #5	$224.89	5.514%	$237.2904	$237.29	$237.30	$237.30
Purchase #6	$162.79	6.362%	$173.1467	$173.15	$173.15	$173.10
Purchase #7	$183.43	12.461%	$206.2872	$206.29	$206.30	$206.30
7 purchase totals =	$1,033.74		$1,134.3565	$1,134.36	$1,134.40	$1,134.30