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	$166.89	10.359%	$184.1781	$184.18	$184.20	$184.20
Purchase #2	$202.49	7.433%	$217.5411	$217.54	$217.55	$217.50
Purchase #3	$216.78	7.537%	$233.1187	$233.12	$233.10	$233.10
Purchase #4	$64.92	12.338%	$72.9298	$72.93	$72.95	$72.90
Purchase #5	$190.39	8.642%	$206.8435	$206.84	$206.85	$206.80
Purchase #6	$53.72	7.143%	$57.5572	$57.56	$57.55	$57.60
Purchase #7	$79.60	3.140%	$82.0994	$82.10	$82.10	$82.10
7 purchase totals =	$974.79		$1,054.2678	$1,054.27	$1,054.30	$1,054.20