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	$220.93	8.695%	$240.1399	$240.14	$240.15	$240.10
Purchase #2	$239.78	10.334%	$264.5589	$264.56	$264.55	$264.60
Purchase #3	$145.63	9.192%	$159.0163	$159.02	$159.00	$159.00
Purchase #4	$102.78	9.784%	$112.836	$112.84	$112.85	$112.80
Purchase #5	$57.31	12.469%	$64.456	$64.46	$64.45	$64.50
Purchase #6	$230.94	11.148%	$256.6852	$256.69	$256.70	$256.70
Purchase #7	$31.75	6.802%	$33.9096	$33.91	$33.90	$33.90
7 purchase totals =	$1,029.12		$1,131.6019	$1,131.62	$1,131.60	$1,131.60