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	$222.63	8.834%	$242.2971	$242.30	$242.30	$242.30
Purchase #2	$155.34	4.774%	$162.7559	$162.76	$162.75	$162.80
Purchase #3	$58.53	4.686%	$61.2727	$61.27	$61.25	$61.30
Purchase #4	$19.39	5.194%	$20.3971	$20.40	$20.40	$20.40
Purchase #5	$88.45	11.668%	$98.7703	$98.77	$98.75	$98.80
Purchase #6	$241.60	9.384%	$264.2717	$264.27	$264.25	$264.30
Purchase #7	$130.41	4.696%	$136.5341	$136.53	$136.55	$136.50
7 purchase totals =	$916.35		$986.2989	$986.30	$986.25	$986.40