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	$74.86	4.740%	$78.4084	$78.41	$78.40	$78.40
Purchase #2	$188.45	5.481%	$198.7789	$198.78	$198.80	$198.80
Purchase #3	$104.25	5.655%	$110.1453	$110.15	$110.15	$110.10
Purchase #4	$220.73	4.309%	$230.2413	$230.24	$230.25	$230.20
Purchase #5	$28.29	13.617%	$32.1422	$32.14	$32.15	$32.10
Purchase #6	$168.45	12.533%	$189.5618	$189.56	$189.55	$189.60
Purchase #7	$213.38	13.760%	$242.7411	$242.74	$242.75	$242.70
7 purchase totals =	$998.41		$1,082.0190	$1,082.02	$1,082.05	$1,081.90