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	$72.61	7.803%	$78.2758	$78.28	$78.30	$78.30
Purchase #2	$66.56	9.648%	$72.9817	$72.98	$73.00	$73.00
Purchase #3	$56.50	11.126%	$62.7862	$62.79	$62.80	$62.80
Purchase #4	$81.42	8.364%	$88.23	$88.23	$88.25	$88.20
Purchase #5	$210.28	11.443%	$234.3423	$234.34	$234.35	$234.30
Purchase #6	$122.27	6.870%	$130.6699	$130.67	$130.65	$130.70
Purchase #7	$172.55	7.863%	$186.1176	$186.12	$186.10	$186.10
7 purchase totals =	$782.19		$853.4035	$853.41	$853.45	$853.40