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	$75.74	8.714%	$82.34	$82.34	$82.35	$82.30
Purchase #2	$83.89	7.402%	$90.0995	$90.10	$90.10	$90.10
Purchase #3	$156.33	4.141%	$162.8036	$162.80	$162.80	$162.80
Purchase #4	$77.82	4.532%	$81.3468	$81.35	$81.35	$81.30
Purchase #5	$104.78	13.228%	$118.6403	$118.64	$118.65	$118.60
Purchase #6	$220.77	12.798%	$249.0241	$249.02	$249.00	$249.00
Purchase #7	$152.77	4.805%	$160.1106	$160.11	$160.10	$160.10
7 purchase totals =	$872.10		$944.3649	$944.36	$944.35	$944.20