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	$195.68	11.644%	$218.465	$218.47	$218.45	$218.50
Purchase #2	$191.40	4.655%	$200.3097	$200.31	$200.30	$200.30
Purchase #3	$68.86	13.317%	$78.0301	$78.03	$78.05	$78.00
Purchase #4	$202.32	8.328%	$219.1692	$219.17	$219.15	$219.20
Purchase #5	$213.91	7.187%	$229.2837	$229.28	$229.30	$229.30
Purchase #6	$31.30	3.124%	$32.2778	$32.28	$32.30	$32.30
Purchase #7	$130.75	4.279%	$136.3448	$136.34	$136.35	$136.30
7 purchase totals =	$1,034.22		$1,113.8803	$1,113.88	$1,113.90	$1,113.90