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	$169.25	4.498%	$176.8629	$176.86	$176.85	$176.90
Purchase #2	$175.29	4.611%	$183.3726	$183.37	$183.35	$183.40
Purchase #3	$54.33	3.348%	$56.149	$56.15	$56.15	$56.10
Purchase #4	$184.43	13.747%	$209.7836	$209.78	$209.80	$209.80
Purchase #5	$60.77	12.139%	$68.1469	$68.15	$68.15	$68.10
Purchase #6	$83.74	7.155%	$89.7316	$89.73	$89.75	$89.70
Purchase #7	$181.32	4.391%	$189.2818	$189.28	$189.30	$189.30
7 purchase totals =	$909.13		$973.3284	$973.32	$973.35	$973.30