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	$222.29	5.610%	$234.7605	$234.76	$234.75	$234.80
Purchase #2	$86.77	5.686%	$91.7037	$91.70	$91.70	$91.70
Purchase #3	$173.57	9.361%	$189.8179	$189.82	$189.80	$189.80
Purchase #4	$180.30	4.417%	$188.2639	$188.26	$188.25	$188.30
Purchase #5	$136.58	11.818%	$152.721	$152.72	$152.70	$152.70
Purchase #6	$200.49	10.861%	$222.2652	$222.27	$222.25	$222.30
Purchase #7	$134.61	3.492%	$139.3106	$139.31	$139.30	$139.30
7 purchase totals =	$1,134.61		$1,218.8428	$1,218.84	$1,218.75	$1,218.90