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	$138.31	10.536%	$152.8823	$152.88	$152.90	$152.90
Purchase #2	$47.78	6.373%	$50.825	$50.83	$50.85	$50.80
Purchase #3	$102.31	3.417%	$105.8059	$105.81	$105.80	$105.80
Purchase #4	$184.61	3.803%	$191.6307	$191.63	$191.65	$191.60
Purchase #5	$75.36	3.530%	$78.0202	$78.02	$78.00	$78.00
Purchase #6	$224.29	8.522%	$243.404	$243.40	$243.40	$243.40
Purchase #7	$209.30	8.114%	$226.2826	$226.28	$226.30	$226.30
7 purchase totals =	$981.96		$1,048.8507	$1,048.85	$1,048.90	$1,048.80