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	$64.45	11.801%	$72.0557	$72.06	$72.05	$72.10
Purchase #2	$165.41	10.773%	$183.2296	$183.23	$183.25	$183.20
Purchase #3	$165.48	12.231%	$185.7199	$185.72	$185.70	$185.70
Purchase #4	$196.93	3.498%	$203.8186	$203.82	$203.80	$203.80
Purchase #5	$100.34	6.770%	$107.133	$107.13	$107.15	$107.10
Purchase #6	$168.64	7.650%	$181.541	$181.54	$181.55	$181.50
Purchase #7	$196.59	12.444%	$221.0537	$221.05	$221.05	$221.10
7 purchase totals =	$1,057.84		$1,154.5515	$1,154.55	$1,154.55	$1,154.50