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	$62.91	13.807%	$71.596	$71.60	$71.60	$71.60
Purchase #2	$169.97	6.873%	$181.652	$181.65	$181.65	$181.70
Purchase #3	$191.86	4.318%	$200.1445	$200.14	$200.15	$200.10
Purchase #4	$53.32	12.279%	$59.8672	$59.87	$59.85	$59.90
Purchase #5	$127.51	8.179%	$137.939	$137.94	$137.95	$137.90
Purchase #6	$220.32	9.262%	$240.726	$240.73	$240.75	$240.70
Purchase #7	$62.53	9.374%	$68.3916	$68.39	$68.40	$68.40
7 purchase totals =	$888.42		$960.3163	$960.32	$960.35	$960.30