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	$244.98	3.537%	$253.6449	$253.64	$253.65	$253.60
Purchase #2	$166.92	12.678%	$188.0821	$188.08	$188.10	$188.10
Purchase #3	$131.31	11.107%	$145.8946	$145.89	$145.90	$145.90
Purchase #4	$65.83	8.809%	$71.629	$71.63	$71.65	$71.60
Purchase #5	$190.96	10.546%	$211.0986	$211.10	$211.10	$211.10
Purchase #6	$168.67	4.130%	$175.6361	$175.64	$175.65	$175.60
Purchase #7	$79.61	3.560%	$82.4441	$82.44	$82.45	$82.40
7 purchase totals =	$1,048.28		$1,128.4294	$1,128.42	$1,128.50	$1,128.30