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	$68.86	5.118%	$72.3843	$72.38	$72.40	$72.40
Purchase #2	$94.37	7.834%	$101.7629	$101.76	$101.75	$101.80
Purchase #3	$65.40	11.128%	$72.6777	$72.68	$72.70	$72.70
Purchase #4	$186.71	13.289%	$211.5219	$211.52	$211.50	$211.50
Purchase #5	$184.71	3.244%	$190.702	$190.70	$190.70	$190.70
Purchase #6	$154.36	6.319%	$164.114	$164.11	$164.10	$164.10
Purchase #7	$168.84	11.668%	$188.5403	$188.54	$188.55	$188.50
7 purchase totals =	$923.25		$1,001.7031	$1,001.69	$1,001.70	$1,001.70