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	$169.73	3.374%	$175.4567	$175.46	$175.45	$175.50
Purchase #2	$212.85	7.298%	$228.3838	$228.38	$228.40	$228.40
Purchase #3	$85.56	6.205%	$90.869	$90.87	$90.85	$90.90
Purchase #4	$143.49	9.210%	$156.7054	$156.71	$156.70	$156.70
Purchase #5	$240.77	5.719%	$254.5396	$254.54	$254.55	$254.50
Purchase #6	$182.90	3.488%	$189.2796	$189.28	$189.30	$189.30
Purchase #7	$171.84	7.654%	$184.9926	$184.99	$185.00	$185.00
7 purchase totals =	$1,207.14		$1,280.2267	$1,280.23	$1,280.25	$1,280.30