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	$90.70	6.398%	$96.503	$96.50	$96.50	$96.50
Purchase #2	$50.69	7.413%	$54.4476	$54.45	$54.45	$54.40
Purchase #3	$224.76	11.626%	$250.8906	$250.89	$250.90	$250.90
Purchase #4	$57.34	11.585%	$63.9828	$63.98	$64.00	$64.00
Purchase #5	$226.33	4.676%	$236.9132	$236.91	$236.90	$236.90
Purchase #6	$98.83	10.654%	$109.3593	$109.36	$109.35	$109.40
Purchase #7	$194.30	10.363%	$214.4353	$214.44	$214.45	$214.40
7 purchase totals =	$942.95		$1,026.5318	$1,026.53	$1,026.55	$1,026.50