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	$177.41	10.654%	$196.3113	$196.31	$196.30	$196.30
Purchase #2	$187.61	5.298%	$197.5496	$197.55	$197.55	$197.50
Purchase #3	$138.36	5.359%	$145.7747	$145.77	$145.75	$145.80
Purchase #4	$176.95	4.581%	$185.0561	$185.06	$185.05	$185.10
Purchase #5	$212.85	5.121%	$223.75	$223.75	$223.75	$223.80
Purchase #6	$188.26	12.257%	$211.335	$211.34	$211.35	$211.30
Purchase #7	$104.49	6.753%	$111.5462	$111.55	$111.55	$111.50
7 purchase totals =	$1,185.93		$1,271.3229	$1,271.33	$1,271.30	$1,271.30