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	$211.86	4.351%	$221.078	$221.08	$221.10	$221.10
Purchase #2	$152.90	3.729%	$158.6016	$158.60	$158.60	$158.60
Purchase #3	$91.89	9.259%	$100.3981	$100.40	$100.40	$100.40
Purchase #4	$190.30	4.450%	$198.7684	$198.77	$198.75	$198.80
Purchase #5	$79.66	7.695%	$85.7898	$85.79	$85.80	$85.80
Purchase #6	$95.60	6.508%	$101.8216	$101.82	$101.80	$101.80
Purchase #7	$173.60	8.355%	$188.1043	$188.10	$188.10	$188.10
7 purchase totals =	$995.81		$1,054.5618	$1,054.56	$1,054.55	$1,054.60