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	$142.91	6.635%	$152.3921	$152.39	$152.40	$152.40
Purchase #2	$60.47	6.290%	$64.2736	$64.27	$64.25	$64.30
Purchase #3	$232.94	4.679%	$243.8393	$243.84	$243.85	$243.80
Purchase #4	$147.84	10.119%	$162.7999	$162.80	$162.80	$162.80
Purchase #5	$144.38	6.700%	$154.0535	$154.05	$154.05	$154.10
Purchase #6	$101.28	7.675%	$109.0532	$109.05	$109.05	$109.10
Purchase #7	$235.56	6.454%	$250.763	$250.76	$250.75	$250.80
7 purchase totals =	$1,065.38		$1,137.1746	$1,137.16	$1,137.15	$1,137.30