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	$225.69	3.430%	$233.4312	$233.43	$233.45	$233.40
Purchase #2	$56.80	9.621%	$62.2647	$62.26	$62.25	$62.30
Purchase #3	$96.46	13.173%	$109.1667	$109.17	$109.15	$109.20
Purchase #4	$119.61	13.446%	$135.6928	$135.69	$135.70	$135.70
Purchase #5	$79.27	12.478%	$89.1613	$89.16	$89.15	$89.20
Purchase #6	$228.61	6.621%	$243.7463	$243.75	$243.75	$243.70
Purchase #7	$154.31	12.711%	$173.9243	$173.92	$173.90	$173.90
7 purchase totals =	$960.75		$1,047.3873	$1,047.38	$1,047.35	$1,047.40