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	$207.27	10.183%	$228.3763	$228.38	$228.40	$228.40
Purchase #2	$161.45	7.364%	$173.3392	$173.34	$173.35	$173.30
Purchase #3	$215.54	10.843%	$238.911	$238.91	$238.90	$238.90
Purchase #4	$20.44	10.220%	$22.529	$22.53	$22.55	$22.50
Purchase #5	$40.59	3.789%	$42.128	$42.13	$42.15	$42.10
Purchase #6	$245.38	6.621%	$261.6266	$261.63	$261.65	$261.60
Purchase #7	$159.57	8.722%	$173.4877	$173.49	$173.50	$173.50
7 purchase totals =	$1,050.24		$1,140.3978	$1,140.41	$1,140.50	$1,140.30