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	$39.68	8.266%	$42.9599	$42.96	$42.95	$43.00
Purchase #2	$81.32	8.776%	$88.4566	$88.46	$88.45	$88.50
Purchase #3	$229.47	6.624%	$244.6701	$244.67	$244.65	$244.70
Purchase #4	$227.38	8.730%	$247.2303	$247.23	$247.25	$247.20
Purchase #5	$117.46	11.789%	$131.3074	$131.31	$131.30	$131.30
Purchase #6	$200.55	7.279%	$215.148	$215.15	$215.15	$215.10
Purchase #7	$162.91	6.444%	$173.4079	$173.41	$173.40	$173.40
7 purchase totals =	$1,058.77		$1,143.1802	$1,143.19	$1,143.15	$1,143.20