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	$46.69	10.864%	$51.7624	$51.76	$51.75	$51.80
Purchase #2	$79.86	12.145%	$89.559	$89.56	$89.55	$89.60
Purchase #3	$131.64	12.122%	$147.5974	$147.60	$147.60	$147.60
Purchase #4	$168.96	8.749%	$183.7423	$183.74	$183.75	$183.70
Purchase #5	$243.47	10.215%	$268.3405	$268.34	$268.35	$268.30
Purchase #6	$52.40	12.742%	$59.0768	$59.08	$59.10	$59.10
Purchase #7	$114.67	12.163%	$128.6173	$128.62	$128.60	$128.60
7 purchase totals =	$837.69		$928.6957	$928.70	$928.70	$928.70